1.3. Il protocollo Internet comunemente chiamato TCP/IP

NOTES ON COMPUTER NETWORKS

We always study, revise and research on what we are passionate for: the web.Here we start a long journey about computer networks trying to simplify as much as possible a very complex subject.

Two computers are interconnected if they can exchange information via a copper wire, fiber optics, microwaves, infrared and satellites.

1.1. Computer network VS distributed system

A computer network is a collection of independent computers while a distributed system appears to its users as a single system.A distributed system is the World Wide Web that goes on top of the Internet and presents a model in which everything looks like a web page.

There are two types of transmission technology that are mostly used:

broadcast links: a packet that goes to all destinations or broadcasting;

point-to-point links: one sender and one receiver or unicasting.

1.2. Networks as a stack of layers that exchange messages

Most networks are organized as a stack of layers or levels, each one built upon the other and offering certain services to the higher layers; the goal is to ensure that each packet will arrive correctly to destination.A service defines what operations the layer above can do.A protocol defines the format to which packet or message can be exchanged between peers.

There are two types of connection between layers:

connection oriented: exactly like the telephone system, before transmitting it is first establishes a connection;

connectionless: exactly like the postal system - each postcard travels through different nodes before arriving at destination.

1.3. The Internet protocol suite commonly known as TCP/IP

Here it is a sketch of what we will describe in later posts.Four layers as mentioned above with services and protocols representing the reference model for the Internet and similar networks.